Purification of alkyl aryl sulfonates



Feb. 25, 1 958 J. w. CONWELL EFAL 2,824,831

PURIFICATION OF ALKYL ARYL SULFONATES 2 Sheets-Sheet 1 Filed Oct. 10, 1956 E 0 mm C! R 0 SP. m EE.

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A T TORNEY Feb. 25, 1958 J. W. CONWELL El AL PURIFICATION OF ALKYL ARYL SULFONATES Filed Oct. 10, 1956 KLETT COLOR OF SODIUM DODECYLBENZENE SULFONATE 2 Sheets-Sheet 2 DECOLORIZING OF SODIUM I40 DODECYLBENZENE SULFONATE BY ELECTROLYSIS.

NO SODIUM CHLORIDE PRESENT SODIUM CHLORIDE ADDED no 0 20 40 so so I00 I20 ELECTROLYSIS TIME MINUTES INVENTORS A 1103mm United States Ptet PURIFICATION or ALKYL ARYL sULroNATEs John W. Conwell and William C. Ziegenhain, Ponca City, Okla, assignors to Continental Oil Company, Ponca City, Okla., a corporation of Delaware Application October 10, 1956, Serial No. 615,080

7 Claims. (Cl. 204-131) The present invention relates to the production of neutral alkyl aryl sulfonates and relates more particularly to the production of neutralized alkyl aryl sulfonates which are substantially free of color bodies.

Sulfonation or alkyl aryl hydrocarbons has generally followed the procedure wherein about 1.3 to 2 parts by weight of 100 to 105 percent sulfuric acid is used per part by weight of the alkyl aryl hydrocarbon. fonating agents have been use but whatever agent was used the resulting mixture upon completion of the sulfonation reaction produced an off-colored sulfonate upon neutralization with a base such as sodium hydroxide; Since such colored sulfonates can only be used in a relatively few applications, various methods have been suggested for removing the color bodies. Light colored sulfonates are particularly desirable in a laundry detergent. Methods as used heretofore have involved treating aqueous solutions ofmetal sulfonates with hydrogen peroxide or other bleaching agent such as alkali peroxide. Other treating agents have included solutions of a metal persalt such as an alkali metal perborate, or an alkali metal persulfate. In addition, aqueous sulfonates have been blown with oxygen or oxidizing gas in order to improve the color of the product. None of these methods have been entirely satisfactory, generally because they have involved an undesirable expenditure of materials and time and furthermore the product so obtained has not been improved greatly in color.

It is therefore, a princpal object of this invention to provide an improved process which process obviates the disadvantages of the prior art methods. It is another object of our invention to provide an improved method of treating neutralized alkyl aryl sulfonic acids whereby substantially colorless sulfonates may be obtained. Further objects and advantages of the invention will become apparent from the following description.

The foregoing objects are attained by the process which involves in brief the following steps. An alkyl aryl hydrocarbon is reacted with a sulfonating agent such as sulfuric acid or oleum. Following sulfonation, the spent sulfonating agent is removed from the mixture comprising the sulfonic acid, and spent sulfonating agent. The recovered alkyl aryl sulfonic acid may be neutralized with a base such as sodium hydroxide to producesodium alkyl aryl sulfonate. Obviously other bases may be-.used, such as alkali and alkaline earth metal oxides, carbonates, etc., for neutralizing the sulfonic acid if desired. Following neutralization a small amount of an alkali halide or an alkaline earth metal halide is added and the resulting mixture (solution or slurry) is subjected to electrolysis which bleaches the product. Alternately, the halide may be added to the recovered alkyl aryl sulfonic acid, the

resulting mixture subjected to electrolysis and the electrolyzed mixture neutralized.

Suitable' alkyl aryl hydrocarbons which may be used are kylating agent in the presence of a Friedel-Crafts type Other sulcatalyst such as boron fluoride, hydrogen fluoride, sulfuric acid, etc. The alkylating agent may be a 9 to 18 carbon straight or branched chain olefin, alcohol or halide. A suitable straight or branched chain olefin is produced from a tetradecane fraction having a boiling range of 240-260 C. which is obtained by fractionating kerosene. Branched chain olefins are preferred, however, as the alkylating agent, such as the 9 to 18 carbon polymers of propylene including trimers, tetramers, pentamers, or mixtures thereof. Other alkylating agents that may be used include the branched chain nonyl, decyl, dodecyl, octadecyl alcohols and chlorides.

A suitable alkyl aryl hydrocarbon which is also available commercially in large quantities is a blend of monoalkylbenzenes sometimes called dodecylbenzene. This particular product is obtainable from Continental Oil Company under the trade name Neolene 400. Typical physical properties of dodecylbenzene or Neolene 400 are as follows:

Specific gravity at 16 C 0.8742

The sulfonating of the alkyl aryl hydrocarbons may be carried out by methods well known to those skilled in the art using sulfuric acid or oleum as the sulfonating agent. Other suitable sulfonating agents which may be used include chlorosulfonic acid, sulfur trioxide, etc. If desired the alkyl aryl hydrocarbon may be diluted with a solvent such as a mineral oil, halogenated hydrocarbon, or surfur dioxide prior to sulfonation.

following the sulfonation of the alkyl aryl hydrocarbon, any spent sulfonating agent present may be removed from the resulting mixture. If desired the mixture prior to the removal of the spent sulfonating agent may be quenched with water, alcohol, or a solution of water and alcohol, or a mineral oil if the product is oil soluble. After removing the spent sulfonating agent the concentration of the alkyl aryl sulfonic acid present in the residue may vary from about 50 to or higher depending upon the relative amounts of sulfonating agent used and the sulfonatable material present.

Although any water soluble metal halide may be used, the chlorides are preferred because they are more economical and are available in greater quantities than the other halides. As to the amount of metal halide, We prefer to add about 0.25 to about 5 percent of the halide based on the weight of the resultant sulfonic acid mixture after the removal of spent sulfonating agent. Mo're particularly, we prefer to use about 1 percent of the metal halide based on the sulfonic acid mixture or on the neutralized sulfonic acid mixture. We have found that the electrolysis of sulfonic acid mixtnres or neutralized sulfonic acid mixtures in the presence of a metal halide results in organic sulfonates of improved color.

The actual voltage and the current flow used in the electrolysis reaction can be varied over a wide range. As for example, excellent results have been obtained wherein the electrolytic E. M. F. and the current density have varied from about 1 to 12 volts and from aboutOJOS to about 1.5 amperes per square decimeter respectively. Variations above and below these values, however, may be Patented F eh. 25, 1958 V V specified v in the appended claims.

used. We have found that an electrical energy of about 7 30 watt hours at a current density of about 0.5 to 1.5 amperes per square decimeter of electrode area will improve vthe color of one pound of neutral surface active forganic sulfonate by one Klett'color'unitwhenthe color 7 lsrneasured on a solution of'the. neutral surface active salt. All Klettco lor determinations .were made;

using a Number 42 blue filter. As to the concentration of the organic sulfonic acid or the organic. sulfonate, that:

may vary from about 5 to 95%. In general, the concentration is limited only by the concentration of the product desired and ease ofhandling the material. In some cases a 40 percent aqueous concentration of the sulfonate may 4 r metal halide was subjected to, electrolysis. Whereas the neutralization product of the une'lectrolyzed sulfonic acid had a Klett color of 156, the neutralized'product of the electrolyzed sulfonic acid had a Klett color .of about 30( EXAMPLE 3 V was electrolyzed for 1 hour in the presence of 1 percent be too viscous to obtain satisfactory mixing, while the salt I of another sulfonated petroleum fraction may. be fluid enough for satisfactory operation'at concentrations as high 7 as 95 percent. As to the temperature employed during the electrolysis reaction,'the solution or slurry temperature may vary from any temperature above the freezing 'pointof the mixture to justbelow its boiling point, as

long as the viscosity 'is such to permit mixing. For con- 7 ve'nierice weprefer to operate within the range of about -60" CI p f r While we do not wish to be bound by any theory as tohow our results are produced, we believe that the correct explanation of these results is substantially'as follows: It has been observed-that no sludge is formed during'the electrolysis reaction and as a consequence we believe that the color bodiesare converted to'colorless materials by the action of nascent hy-pohalite produced byelectrolysjisa e V V 7 We have found that the-material of-which the electrodes are constructed is critical Any material which is suitable for the construction of the electrodes used in the electrolysis of aqueous sodium chloride solution is a suit- 'able electrode material in our process also. We prefer to 'use'carbon anodes and platinum cathodes.

In order to disclose the nature of the present invention still more clearly, the following illustrative examples will be given. 'It is to be understood that the invention is not to be limited to the specific conditions or details set forth j in these examples exceptinsofar as such limitations are Parts given are parts.

by weight. V j

a EXAMPLE 1' i I T0100 parts of a 6% aqueous solution of dodecylbenzene sulfonic acid was added l part of sodium chloride and the solution added to an electrolylic cell having a positive platinum electrode surface of 95 7 square centimeters. A current of 1 ampere at an of '10 volts was passed through the cell. During the electrolysis the temperature was maintained at approximately '25 C. Samples were periodically withdrawn, from the cell, neutralized with sodium hydroxide and the Klett color determined. The results are summarized in Table l and Figure 1.

I Table 1 Electrolysis Time, Minutes Klett Color 0 165 m 154 20 a e r 140 7 so 7 V 7 I 124 .40 110 ,100 60 V V so 120 I 85 The use of a higher current density resulted in reduced time requirements for attainment of equivalent colorreductions. 7 7

EXAMPLE 2 Example 1 was repeated with the exception'that a 10% solution of dodecylbenzene' sulfonic acid containing no sodium chloride or other alkali metal or alkaline earth sodium chloride the Klett color'was reducedat 80.

' EXAMP EW A '10 percent solution of sodium .dodecylbenzene' sula i fo nate having Klett color of 132 was subjected to electrolysis with and without 1 percent 'of added sodium chloride. Periodically samples were withdrawn from the electrolysis cell and the Klett color determined. The

results are summarized inTable 2 and Figure 2. Table 2 -Klett Color Eleetrolysis Time, Minutes EXAMPLE 5 7 V 7 In this example 100 parts of a 10' percent} aqueous solution of dodecyl benzene 'sulfonic acid and '100 parts of a 10 percent'aqueous solution of sodium dodecylbenzene sulfonate were each subjected to electrolysis in the presencejof 1 part of the various metal halides listed below. In the electrolysis reaction a current of 2 amperes at an E. M. F. of '10 volts was passed throughfthe'cell at 25 C. for a period of l hou'r. At the end of the hour a sample of the productwas withdrawn from the'f cell, neutralized with sodium hydroxide if necessary, and the Klett color determined. Neutralization is only necesi V .sary when dodecylbenzene sulfonic acid is subjected to The experiments, and the; Klett color of f electrolysis. q 7 I the product both beforefand after electrolysis are sum- 7 marized in Table 3 below.

Table 3 Klett Color. i

y Metal Chloride Used Dodeeylbenzene Sodiuni'Dodecylv i V Sulionic Aeid' benezeneSulfona-te Before After Before 7 After I Calcium Chloride. V 19 Lithium Chloride 461 193 v 173 68 Ferric Chloride 442 173 1 197 94 Sodium Fluoride 442 360 i196 179 Potassium Chlor 700 680 147 Cupric Chloride--. 462 329 204 132 Manganous Chlon 508 402' 188 137 Magnesium Chloride 220 133' 193 7 147 Ammonium Ohloridm. 468 442 w 233 2Q0 *Not attempted since e. stable emulsion ,was for ed, it was not possible to obtain anaocurate mett color. V V

The process as described above may beoperated either as a batch or as a continuous process, f helljatter is. "used the alkyl aryl sulfonic acidfior the corresponding salt, 7

.water, and metal'halideis cauSedto flow'throughthe electrolyticgcell at such alrate. that the resident time of the components in the cell is suflicient to efiect the desired bleaching.

Although the examples given above are specified to dodecylbenzene sulfonic acid or the corresponding salt our invention is not so limited but can be used for the improvement in color of other sulfonic acids and sulfonates. As additional examples the product known as dodecylbenzene intermediate sulfonic acid and the corresponding salt was improved in color by the procedure of this invention. We prefer to use sodium or potassium chloride as the specific metal halide when this particular alkyl aryl sulfonic acid or sulfonate is subjected to electrolysis. Dodecylbenzene intermediate sulfonic acid is obtained by sulfonating the hydrocarbon known as dodecylbenzene intermediate. Its typical physical properties are as follows:

Gravity, AP 40.4 Average molecular weight 193 Percent sulfnnatahle 57 A. S. T. M., .D-l58 Engler distillation:

I. B. P F 353 F 371 50 F 393 90 T... 433 95 F 448 F. B. P F 488 Refractive index at 25 C 1.4688 Viscosity at 100 F centipoises 1.33 Aniline point F- 82 While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. A process of bleaching an organic compound selected from the group consisting of an alkyl aryl sulfonic acid and a salt thereof which comprises subjecting an aqueous mixture of said organic compound to electrolysis in the presence of a metal halide, at an E. M. F. within the range of 1 to 12 volts and at a current density varying from 0.05 to 1.5 amperes per square decimeter.

2. The process of claim 1 wherein the organic compound is dodecylbenzene sulfonic acid.

3. The process of claim 1 wherein the organic compound is sodium dodecylbenzene sulfonate.

4. The process of claim 1 wherein the metal halide is sodium chloride.

5. The process of claim 1 wherein the metal halide is calcium chloride.

6. The process of claim 1 wherein the organic compound is dodecylbenzene intermediate sulfonic acid.

7. The process of claim 1 wherein the organic com pound is sodium dodecylbenzene intermediate sulfonate.

Webber et a1. Aug. 8, 1933- Toone Nov. 9, 1943 

1. PROCESS OF BLEACHING AN ORGANIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF AN ALKYL ARYL SULFONIC ACID AND A SALT THEREOF WHICH COMPRISES SUBJECTING AN AQUEOUS MIXTURE OF SAID ORGANIC COMPOUND TO ELECTROLYSIS IN THE PRESENCE OF A METAL HALIDE, AT AN E. M. F. WITHIN 